Eritrea said on Monday it had not renewed the residence permits of 13 foreign Catholic missionaries, but it denied reports it had expelled them.

Several Catholic news websites reported that the Red Sea state on Nov 6 gave the missionaries two weeks to leave but gave no reason for the action.

"This is an ordinary issue of immigration. Their residence permits expired and they were not renewed," presidential adviser Yemane Ghebremeskel told Reuters by telephone. "Expulsion does not even apply. They have not been expelled."

Yemane did not give the nationalities of the missionaries.

About half of Eritrea's 4.6 million people are Christian and half Muslim, but only religious groups officially registered with the government can practise.

The government closed all churches in 2002 except Orthodox, Catholic, evangelical ones and Islam, human rights groups say.

Eritrea routinely denies persecuting anyone on the basis of faith, but has been accused by human rights groups and the U.S. State Department of violating religious freedoms.

Foreign religious groups have criticised Asmara over the appointment of a new head of the Eritrean Orthodox Church and the arrest of some 80 people in May, including several U.S. citizens, in a raid on a religious ceremony.

Eritrea accuses what it calls "fringe" religious groups of sowing dissent and defends its right to arrest members who assemble illegally.